Insects developed wings around the same time plants began growing upward — more than 100 million years before the first reptiles flew [sources: Meyer, Yeates]. The closest modern equivalents to these pioneers of flight are mayflies and dragonflies, although ancient dragonflies sported 24- to 28-inch (60- to 70-centimeter) wingspans [source: Yeates]!
Flight helps insects spread into new areas, migrate, escape predators and reach out-of-the-way food sources. Some sportier models of insect come equipped with foldable wings, a handy trait for squeezing into tight spaces like nests or tunnels [source: Danforth].
Insects are the only invertebrates that fly. They're also the only winged animals that did not give up a set of limbs in order to gain wings [sources: Meyer, Yeates]. The speed and agility they display in flight, the heavy loads they can carry, and the strange flight mechanics involved continue to inspire research by physicists and aeronautical engineers [source: Meyer].
When flying, insects use about as much energy (calories per unit of lift) as do birds and bats, but they excel at converting that energy into power. Insects store and release energy with spring-like efficiency because their bodies are both flexible and resilient, thanks in part to their exoskeletons [source: Meyer].